Cyclictest
Cyclictest is a high resolution test program, written by User:Tglx, maintained by User:Clark Williams
Contents |
Documentation
Installation
Get the latest sources from the git repository, do a git clone git://git.kernel.org/pub/scm/linux/kernel/git/tglx/rt-tests.git or fetch a released tarball from the archive, untar into a directory of your choice and run make in the source directory. If you want to cross compile, just run make CROSS_COMPILE=<your-compiler-prefix> (for example make CROSS_COMPILE=arm-v4t-linux-gnueabi-).
You can run the resulting binary from there or install it.
Run it
Make sure to be root or use sudo to run cyclictest.
Without parameters cyclictest creates one thread with a 1ms interval timer.
cyclictest -h provides help text for the various options
[lgs@f11 rt-tests]# [lgs@f11 rt-tests]# [lgs@f11 rt-tests]# ./cyclictest --help cyclictest V 0.42 Usage: cyclictest <options>
-a [NUM] --affinity run thread #N on processor #N, if possible
with NUM pin all threads to the processor NUM
-b USEC --breaktrace=USEC send break trace command when latency > USEC -B --preemptirqs both preempt and irqsoff tracing (used with -b) -c CLOCK --clock=CLOCK select clock
0 = CLOCK_MONOTONIC (default)
1 = CLOCK_REALTIME
-C --context context switch tracing (used with -b) -d DIST --distance=DIST distance of thread intervals in us default=500 -E --event event tracing (used with -b) -f --ftrace function trace (when -b is active) -i INTV --interval=INTV base interval of thread in us default=1000 -I --irqsoff Irqsoff tracing (used with -b) -l LOOPS --loops=LOOPS number of loops: default=0(endless) -m --mlockall lock current and future memory allocations -n --nanosleep use clock_nanosleep -N --nsecs print results in ns instead of ms (default ms) -o RED --oscope=RED oscilloscope mode, reduce verbose output by RED -O TOPT --traceopt=TOPT trace option -p PRIO --prio=PRIO priority of highest prio thread -P --preemptoff Preempt off tracing (used with -b) -q --quiet print only a summary on exit -r --relative use relative timer instead of absolute -s --system use sys_nanosleep and sys_setitimer -T TRACE --tracer=TRACER set tracing function
configured tracers: unavailable (debugfs not mounted)
-t --threads one thread per available processor -t [NUM] --threads=NUM number of threads:
without NUM, threads = max_cpus
without -t default = 1
-v --verbose output values on stdout for statistics
format: n:c:v n=tasknum c=count v=value in us
-D --duration=t specify a length for the test run
default is in seconds, but 'm', 'h', or 'd' maybe add
ed
to modify value to minutes, hours or days
-h --histogram=US dump a latency histogram to stdout after the run
US is the max time to be be tracked in microseconds
-w --wakeup task wakeup tracing (used with -b) -W --wakeuprt rt task wakeup tracing (used with -b)
-b is a debugging option to control the latency tracer in the realtime preemption patch.
It is useful to track down unexpected large latencies on a system. This option does only work with
- CONFIG_PREEMPT_RT=y
- CONFIG_WAKEUP_TIMING=y
- CONFIG_LATENCY_TRACE=y
- CONFIG_CRITICAL_PREEMPT_TIMING=y
- CONFIG_CRITICAL_IRQSOFF_TIMING=y
kernel configuration options enabled. The USEC parameter to the -b option defines a maximum latency value, which is compared against the actual latencies of the test. Once the measured latency is higher than the given maximum, the kernel tracer and cyclictest is stopped. The trace can be read from /proc/latency_trace
mybox# cat /proc/latency_trace >trace.log
Please be aware that the tracer adds significant overhead to the kernel, so the latencies will be much higher than on a kernel with latency tracing disabled.
-c CLOCK selects the clock, which is used
- 0 selects CLOCK_MONOTONIC, which is the monotonic increasing system time. This is the default selection
- 1 selects CLOCK_REALTIME, which is the time of day time.
CLOCK_REALTIME can be set by settimeofday, while CLOCK_MONOTONIC can not be modified by the user.
This option has no influence when the -s option is given.
-d DIST set the distance of thread intervals in microseconds (default is 500us)
When cylictest is called with the -t option and more than one thread is created, then this distance value is added to the interval of the threads.
Interval(thread N) = Interval(thread N-1) + DIST
-i INTV set the base interval of the thread(s) in microseconds (default is 1000us)
This sets the interval of the first thread. See also -d.
-l LOOPS set the number of loops (default = 0(endless))
This option is useful for automated tests with a given number of test cycles. cyclictest is stopped once the number of timer intervals has been reached.
-n use clock_nanosleep instead of posix interval timers
Setting this option runs the tests with clock_nanosleep instead of posix interval timers.
-p PRIO set the priority of the first thread
The given priority is set to the first test thread. Each further thread gets a lower priority:
Priority(Thread N) = Priority(Thread N-1)
-q run the tests quiet and print only a summary on exit
Useful for automated tests, where only the summary output needs to be captured
-r use relative timers instead of absolute
The default behaviour of the tests is to use absolute timers. This option is there for completeness and should not be used for reproducible tests.
-s use sys_nanosleep and sys_setitimer instead of posix timers
Note, that -s can only be used with one thread because itimers are per process and not per thread. -s in combination with -n uses the nanosleep syscall and is not restricted to one thread
-t NUM set the number of test threads (default is 1), -t without an argument makes the number of threads equal to the number of cpus
Create NUM test threads. See -d, -i and -p for further information.
-v output values on stdout for statistics
This option is used to gather statistical information about the latency distribution. The output is sent to stdout. The output format is
n:c:v
where n=task number c=count v=latency value in us
Use this option in combination with -l
The OSADL Realtime LiveCD project provides a script to plot the latency distribution.
Expected Results
tglx's reference machine
All tests have been run on a Pentium III 400MHz based PC.
The tables show comparisons of vanilla Linux 2.6.16, Linux-2.6.16-hrt5 and Linux-2.6.16-rt12. The tests for intervals less than the jiffy resolution have not been run on vanilla Linux 2.6.16. The test thread runs in all cases with SCHED_FIFO and priority 80. All numbers are in microseconds.
- Test case: clock_nanosleep(TIME_ABSTIME), Interval 10000 microseconds,. 10000 loops, no load.
Commandline: cyclictest -t1 -p 80 -n -i 10000 -l 10000
| Kernel | min | max | avg |
| 2.6.16 | 24 | 4043 | 1989 |
| 2.6.16-hrt5 | 12 | 94 | 20 |
| 2.6.16-rt12 | 6 | 40 | 10 |
- Test case: clock_nanosleep(TIME_ABSTIME), Interval 10000 micro seconds,. 10000 loops, 100% load.
Commandline: cyclictest -t1 -p 80 -n -i 10000 -l 10000
| Kernel | min | max | avg |
| 2.6.16 | 55 | 4280 | 2198 |
| 2.6.16-hrt5 | 11 | 458 | 55 |
| 2.6.16-rt12 | 6 | 67 | 29 |
- Test case: POSIX interval timer, Interval 10000 micro seconds,. 10000 loops, no load.
Commandline: cyclictest -t1 -p 80 -i 10000 -l 10000
| Kernel | min | max | avg |
| 2.6.16 | 21 | 4073 | 2098 |
| 2.6.16-hrt5 | 22 | 120 | 35 |
| 2.6.16-rt12 | 20 | 60 | 31 |
- Test case: POSIX interval timer, Interval 10000 micro seconds,. 10000 loops, 100% load.
Commandline: cyclictest -t1 -p 80 -i 10000 -l 10000
| Kernel | min | max | avg |
| 2.6.16 | 82 | 4271 | 2089 |
| 2.6.16-hrt5 | 31 | 458 | 53 |
| 2.6.16-rt12 | 21 | 70 | 35 |
- Test case: clock_nanosleep(TIME_ABSTIME), Interval 500 micro seconds,. 100000 loops, no load.
Commandline: cyclictest -t1 -p 80 -i 10000 -n -l 100000
| Kernel | min | max | avg |
| 2.6.16-hrt5 | 5 | 108 | 24 |
| 2.6.16-rt12 | 5 | 48 | 7 |
- Test case: clock_nanosleep(TIME_ABSTIME), Interval 500 micro seconds,. 100000 loops, 100% load.
Commandline: cyclictest -t1 -p 80 -i 500 -n -l 100000
| Kernel | min | max | avg |
| 2.6.16-hrt5 | 9 | 684 | 56 |
| 2.6.16-rt12 | 10 | 60 | 22 |
- Test case: POSIX interval timer, Interval 500 micro seconds,. 100000 loops, no load.
Commandline: cyclictest -t1 -p 80 -i 500 -l 100000
| Kernel | min | max | avg |
| 2.6.16-hrt5 | 8 | 119 | 22 |
| 2.6.16-rt12 | 12 | 78 | 16 |
- Test case: POSIX interval timer, Interval 500 micro seconds,. 100000 loops, 100% load.
Commandline: cyclictest -t1 -p 80 -i 500 -l 100000
| Kernel | min | max | avg |
| 2.6.16-hrt5 | 16 | 489 | 58 |
| 2.6.16-rt12 | 12 | 95 | 29 |
External Links
FAQ
ps shows the wrong scheduling class SCHED_OTHER
Each cyclictest-task consist of one or more threads. ps -ce shows only the main-process not the threads of the main-process. ps -eLc | grep cyclic shows the main-process an the containing threads with the correct scheduler class SCHED_FIFO.
#>./cyclictest -t5 -p 80 -n -i 10000 #> ps -cLe | grep cyclic 4764 4764 TS 19 pts/1 00:00:01 cyclictest 4764 4765 FF 120 pts/1 00:00:00 cyclictest 4764 4766 FF 119 pts/1 00:00:00 cyclictest 4764 4767 FF 118 pts/1 00:00:00 cyclictest 4764 4768 FF 117 pts/1 00:00:00 cyclictest 4764 4769 FF 116 pts/1 00:00:00 cyclictest
chrt shows the wrong scheduling class SCHED_OTHER
Don't use the PID of the main-process, but the pid of one of the threads from the main-process. The threads are shown with ps -cLe | grep cyclic.
#> chrt -p 4766 pid 4766's current scheduling policy: SCHED_FIFO pid 4766's current scheduling priority: 79
